Organic pressure-sensitive adhesives have been finding increased utility principally to manufacture pressure sensitive adhesive tapes. For a variety of common uses, pressure-sensitive adhesive tapes manufactured with organic pressure-sensitive adhesives, have the requisite physical properties and low cost to make them very much in demand.
However, there are many uses for which pressure-sensitive tapes manufactured from organic pressure-sensitive adhesives are unsuitable. For example, organic pressure-sensitive adhesives tapes do not weather well. Such tapes have poor adhesion to low energy surfaces. These tapes have poor low temperature flexibility, and they have poor high temperature stability. Thus, organic pressure-sensitive adhesive tapes are generally unsuitable for use in outside graphics, such as striping on automobiles or graphics in windows; for use in bonding plastics and for use in conditions where temperature extremes are encountered.
Silicone pressure-sensitive adhesives are also well known adhesives and are widely employed in a variety of uses, including pressure-sensitive adhesive tape. Silicone pressure-sensitive adhesives exhibit excellent adhesion to very low energy surfaces, have excellent weatherability, are flexible at low temperture and are chemically stable at very high temperature. However, the principal drawback to a much wider spread use of silicone pressure-sensitive adhesives is cost.
Thus, the present day market in pressure-sensitive adhesives is split between high performance but costly silicone pressure-sensitive adhesives and organic pressure-sensitive adhesives which are cost effective for most uses. Of course, attempts have been made to obtain pressure-sensitive adhesives which have intermediate physical properties as well as intermediate price.
Principally, such attempts have involved blending a solution of silicone pressure-sensitive adhesive and a solution or organic pressure-sensitive adhesive and applying the blend to a tape from solution. This method has two principal drawbacks. Firstly, the silicone adhesive and the organic adhesive are incompatible. Thus, during solvent removal after application, the adhesives at some point must precipitate from solution and if solvent is not removed quickly enough, phase separation will occur. Secondly, this method requires that the two adhesives be applied from solution which obviously requires a solvent. In this case the solvent is organic solvent, the emission of which is coming under increasing regulation by both federal, state and local governments.
It is an object of the present invention to manufacture silicone and organic pressure-sensitive adhesive blends without the use of organic solvents.
It is another object of the present invention to manufacture silicone and organic pressure-sensitive adhesive blends from a water emulsion.
It is still another object of the present invention to produce a water emulsion containing silicone pressure-sensitive adhesives and organic pressure-sensitive adhesives.